Small animal, particularly rodent, euthanasia is commonly performed by placing the animals in a chamber that is connected to a carbon dioxide tank and allowing the gas to flow until the animals are euthanatized as measured by cessation of heartbeat and respiration.
It is commonly accepted that euthanasia of animals should be conducted effectively in a painless manner and without causing excessive excitation of the animal. Various methods of euthanasia have been described in the literature. The methods include mechanical and electrical means as well as inhalation of gases and administration of anesthetic fluids. For example, see Vet. Rec. 116, 416 (1985) and Comp. Med. 53(3) 249-257 (2002).
Gas inhalation has been endorsed as the most efficient way of euthanitizing large numbers of small animals, including but not limited to rodents, such as mice, rats, guinea pigs, and others. Carbon dioxide is the most widely used gas for euthanasia of rodents and is on the list of acceptable agents recommended by the American Veterinary Medical Association (AVMA) as described in J. Am. Vet. Med. 202(2): 229-249 (1996).
Despite the fact that carbon dioxide is widely used for rodent euthanasia, questions have arisen regarding its use for humane euthanasia because of alleged concerns that asphyxiation or hypoxia may precede anesthesia as described in Lab. Anim. 223:220-228 (1989). According to the AVMA, the suitability of a method or apparatus for euthanasia depends on whether an animal experiences distress between the time it begins to inhale the euthanisizing agent and the time it loses consciousness.
Distress is an aversive state in which the animal is unable to adapt to stressors and the resulting distress presents as maladaptive behaviors exemplified but not limited to struggling, attempts to escape, salivation, urination and reflex muscle contractions such as tremors, shivers and spasms.
Due to lack of automation and operator error prior art processes lack standardization and compliance with the Animal Welfare Act. Despite the widespread use of carbon dioxide in the euthanasia of laboratory animal species, considerable controversy exists concerning whether distress is associated with carbon dioxide induction, as studies have produced contradictory results as to whether a high level of distress was experienced by rodents prior to loss of consciousness. Another area of controversy is whether the stress level of the animal is increased if the chamber is pre-filled or post-filled with gas before the process is initiated.
Based on the foregoing, it is an objective of the present invention to provide a method of and apparatus for gaseous euthanasia of animals which is humane, painless and does not induce fear or apprehension in the animal. It is a further objective that the method and apparatus be reliable, cost-effective, provide a high standard of compliance for the operator, and be safe and easy to operate. The device of the present invention advantageously minimizes operator input as to gas flow rates and times and actual handling of the animals themselves resulting in the reduction of operational and compliance issues.